"The agreement was signed by top defence officials from Pakistan and Russia in Rawalpindi on Wednesday," Dawn cited a military source as saying.
Both countries were negotiating the deal for the past year, signalling a major thaw in relations between the two Cold War rivals.
Chief of Army Staff General Raheel Sharif visited Russia in June, after which a draft contract for the delivery of four Mi-35M 'Hind E' combat helicopters was sent to Pakistan from Russia.
General Raheel Sharif spent about 15 hours at an arms expo which featured Russia's cutting-edge weapons and military equipment.
Late last year, Russian Defence Minister Sergei Shoigu undertook a visit to Pakistan to discuss bilateral defence cooperation with the Pakistani leadership.
The CEO of Russia's Rostec corporation, Sergey Chemezov, had also said Russia had lifted its embargo on delivery of military hardware and armaments to Pakistan and negotiations were being held on delivering helicopters.
Pakistan currently has a number of 'Mi-17' helicopters delivered by the US to assist in the fight against militancy.
The Mi-35 helicopter is an exceedingly modernised version of the Mi-24 combat helicopter with new onboard equipment and avionics. It also has a more powerful engine and a different tail rotor.
Pakistan and Russia signed a bilateral defence cooperation agreement aimed at strengthening military-to-military relations in November last year.